The present invention relates to a lumbar support, and more particularly to a lumbar support for a seat back.
Lumbar supports have long been used to improve the comfort of conventional seats. Typically, the lumbar support is located in a lower portion of a seat back where it extends outwardly to provide support for the lower back or lumbar region. A lumbar support is usually provided with a regulator or control knob that allows the user to select the desired extension of the lumbar support.
A typical lumbar support includes a flexible support platform that is suspended within a seat back. Operation of a control knob located on the exterior of the seat allows the user to selectively draw together opposite ends of the support platform, thereby causing the platform to bow or flew into the lower back region. U.S. Pat. No. 4,627,661 to R onnhult et al discloses a chair back with an adjustable lumbar support. The R onnhult lumbar support includes a support platform having a number of horizontal connecting wires extending between a pair of vertical, flexible, rod-like side elements. A pair of tensioning members extend along opposite vertical edges of the support member. The two tensioning members are interconnected by a threaded shaft which, when rotated in a first direction, draws the tensioning members together, and, when rotated in the opposite direction, moves them farther apart. When the tensioning members are drawn together, they exert a compression or buckling force on the support platform which causes it to bow or flex outward into the lower back region.
Another typical lumbar support is disclosed in PCT Application No. WO 93/13696, published Jul. 22, 1993. This lumbar support includes upper and lower support platforms that are hingedly connected to one another. A tensioning device is provided to apply a compression force to the support platforms. The compression force draws the free ends of the two platforms together, thereby causing the interconnected edges to hinge outwardly into the lower region of the chair back.
These prior art lumbar supports have a relatively large vertical profile. As a result, they occupy a large portion of the seat back. In addition, the outward bowing or arching of the lumbar support causes a bulge of increasingly acute angle. Consequently, the support platform and seat cushioning must be specially adapted to prevent discomfort. Further, the forward deflection of the lumbar support is limited by the physical characteristics of the support platform.